This invention relates to tools such as cutting, drilling, shaping and wire drawing tools and more particularly to tool components comprised of diamond compacts.
Particle is defined as an individual abrasive crystallite or fragment thereof.
A cluster compact is defined as a cluster of abrasive particles bonded together either (1) in a self-bonded relationship, (2) by means of a mechanical or chemical bonding medium disposed between the crystals, (3) by means of some combination of (1) and (2). Reference can be made to U.S. Pat. Nos. 3,136,615; 3,233,988; and 3,690,818 for a detailed disclosure of certain types of cluster compacts and methods for making same. (The disclosures of these patents are hereby incorporated by reference herein.)
A composite compact is defined as a cluster compact bonded to a substrate material such as cemented tungsten carbide. The bond to the substrate can be formed either during or subsequent to the formation of the cluster compact. It is, however, highly preferred to form the bond during formation of the cluster compact. Reference can be made to U.S. Pat. Nos. 3,743,489; 3,745,623; 3,767,371; and 3,831,428 for a detailed disclosure of certain types of composite compacts and methods for making same. (The disclosures of these patents are hereby incorporated by reference herein.)
Before the invention of diamond compacts, large single crystal natural diamond was used in the most severe machining, wire drawing and drilling applications. A primary object of the development of diamond compacts was to replace the large single crystal natural diamonds with a polycrystalline mass in these applications. To do this it was necessary to produce a polycrystalline mass with properties which at least approximate or, more desirably, improve over that of single crystal diamond. This has been essentially achieved. For example, single crystal diamond is sensitive to fracture and chippage along certain planes, thereby requiring precise orientation to maximize its life. A compact, because of its polycrystalline nature, is highly resistant to fracture and chippage and does not require orientation as its properties are non-directional. Also, compacts produced in accordance with the invention set forth in U.S. Pat. No. 3,745,623 have been made with a hardness of between 5,000 and 8,000 knoop hardness at a 3,000 gram load which is approximately 60 to 100% of the hardness of single crystal diamond. The most important factor in producing compacts which have properties competitive with single crystal diamond is the ability to achieve extensive self-bonding or diamond-to-diamond bonding within the compact. Even with the quality of compact products now produced with prior art techniques, the utility and life of such compacts would be improved if more extensive diamond-to-diamond bonding could be achieved. This, of course, would have a significant impact on the commercial success of such a product.
Another approach to making compacts more competitive with single crystal would be to reduce the cost of production. Prior art compacts are produced by a process requiring severe HP/HT conditions. Such processes are inherently expensive thereby yielding expensive products because of the sophisticated apparatus necessary to achieve and maintain such conditions for a sufficient period of time to produce a strong integral compact. It has been found that the degree of self-bonding achieved increases with time of exposure of the compact to HP/HT conditions or with an increase in the HP conditions. However, increases in the exposure time or the HP conditions can mean significantly increased cost of manufacture because of a reduction in life of the HP/HT apparatus used in the process.
Accordingly, it is an object of this invention to provide an improved diamond compact by increasing the degree of self-bonding or diamond-to-diamond bonding present in the compact.
Another object of this invention is to provide an improved process for making diamond compacts whereby a high degree of diamond-to-diamond bonding is achieved at less severe HP/HT conditions or at HP/HT values similar to that of the prior art but which are maintained for a shorter period of time.